The present invention relates to a technique of a liquid crystal display(LCD) in which an electric field is parallel to surfaces of a pair of substrates between which the liquid crystal is interposed and more particularly to a structure of electrodes of the wide viewing angle LCD, which is capable of solving a color shift dependent on a viewing angle in such LCD.
Conventionally, the LCD employing Nematic liquid crystal is widely used as a segment type display such as a watch or a calculator. A transparent substrate composing the LCD, has a switching device as an active element for selectively driving a pixel electrode applying a voltage to the liquid crystal. The color filters of red, blue and green are provided as the color display device. The LCD is classified into an active drive type twisted Nematic(TN) mode in which the Nematic liquid crystal molecule has 90.degree. twisted angle and a multiple drive super twisted Nematic(STN) mode using a rapid relation between a transmittance and a voltage applied to the liquid crystal by twisting the Nematic liquid crystal molecule over 90.degree.. Among two modes, TN mode LCD was conventionally and widely used.
However, in such TN mode LCD, since the liquid crystal molecule has an index of refraction anisotropy and is slantly arranged with respect to the substrate, a contrast of the displayed image is highly dependent on the viewing angle. One of the research for solving the narrow viewing angle is an In-Plane Switching(IPS) mode LCD.
The cell of the IPS mode LCD includes a lower substrate and a upper substrate between which a liquid crystal molecules are interposed, a pixel electrode and a counter electrode formed on the lower substrate and vertical alignment films formed on the lower substrate and the upper substrate. The liquid crystal molecule is driven along the electric field generated between the electrodes on the lower substrate. When no voltage is applied to the IPS mode LCD, the liquid crystal molecules are vertically arranged to the substrate between two substrates by the vertical alignment, so the polarization films whose polarization axis are across to each other and attached on the rear surfaces of the lower substrate and the upper substrate, block the light incident to the substrate(normally black mode). In applying the voltage, the liquid crystal molecules rotate toward the electric field so as to form about 45.degree. with the polarization axis of the polarization film, so the light leakage of the LCD happens. As shown in FIG. 1, the conventional IPS mode LCD has a problem of a color shift dependent on the viewing angle. In other words, since, when the voltage is applied, the liquid crystal molecules are arranged in a specific single direction, the screen of the LCD at the minor axis of the liquid crystal molecule takes a blue and the screen of the LCD at the major axis of the liquid crystal molecule takes a yellow. Accordingly, the quality of the LCD panel is degraded.